Rock drill



July 31, 1928.

J. KHLEN ROCK DRILL Filed Jan. 20, 1923 A ttofJzeg/s Patented July 3l, 1928.

UNITED STATESv 1,678,985 PATENT OFFICE.

' JOSEF KVHLEN, OF HERNE, GERMANY.

Boex DRILL.

Application lied January 20, 1923, Serial No. 613,889, and. in France November` 17, 1222.

My present invention relates to rock drills and more particularly to pneumatic rock drills with reciprocating valves, i. e. valves whose reciprocating valve body may have the shape of a ball,`a iiap, a poppet, or of any other convenient configuration adapted to direct the motive fluid alternately to both faces of the reciprocating piston. In rock drills of this kind it frequently happens that the reciprocating piston does not Iattain its full stroke, because leakages between the valve and the valve seat permit the motiver fluid to continue to flow into vthe'cylinder when theoretically the admission of they motive fluid should have ceased, for which reason the counteracting compression setsV in too early. The result of this incorrect action is that the stroke of the piston, and in consequence thereof that of the percussion bar attached thereto, is shortened to an undesirable extent. Now then, since the percussion bar is utilized in a well-known manner as av means to impart after each blow a certain amount of partial rotation to the drill in order to effectively bring the drill into operativeposition for the next blow, this partial rot-ation of the drill must likewise of necessity fall short of the requiredk extent .when the pistonstroke is unduly shortened. The iinal result of these shortcomings is that the drill gets jammed up in the bore hole and thus becomes inoperative.

My present invention avoids these drawbacks by means of small by-pass. channels arranged in the cylinder wall in the direction of the piston travel. These by-pass channels are made to cooperate with annular channels cut into the periphery of the piston and thus connect the cylinder chambers again withwtheir exhaust ports after the latter havebeen fully shut off from their cylinder chambers preparatory to the` compression.V This after-exhaust of spent motive fluid from said cylinder chambers, on account of the full length otvthe piston strokev secured hereby, increases not only the percussive force of the percussion bar but also assures a jerkless operationv of the rock drill, because' the formation` of the aircusliion for braking 'purposes Y.previous to the reversal of the piston is now executed more regularly than formerly and is accomplished in fullaccordance with vthe true adiabatic curve. ,f .Y

It is, however, necessary that the diameter of the by-pass channels v employed to too large in order to avoid the loss of too much live motive fluid, because during theV admission of livey motive fluid to the reversed piston these by-pass channels connect the.

cylinder chambersv for a second time with the exhaust ports, so that a loss of live motive fluid, however' small, is unavoidable. Although the exhaust ports are hereby opened for an instant only, since at this moment the piston has already attained its highest velocity, the length o' these by-pass channels must nevertheless be such that the exhaust of live motive fluid does not` annul the advantage secured by a suificiently extended after-exhaust. y i

In the accompanying drawing the invention is illustrated as applied to a pneumatic rock drilll Fig. `1 being a longitudinal section, and Fig. 2 a cross section.

c In the cylinder 1 of the rockdrill shown,

a reciprocatingworking piston2 is ar-` Vcylinder chamber 7, vwhereas the opening in:

the seat 6 is similarly connected with the annular cylinder chamber r8. The" kmotive fluid,`in this case compressed air', is admitted to said ball-valve 4 through perforations 9 arranged in the wall of thevalve-chamber 4;. The cylinder 1 is closed attlie top by aA handled cylindercover 10l and atthe'bottomby means of a casing 11. The latter guides the percussion bar 3 and contains a sleeve 12 which in connection with a tool holder and ratchet mechanism of wellv known character, such as shown in Fig.. 2 imparts to the drill-not shown in the drill socket 13-during the return stroke of piston and percussion bar a partial rotation, required to enable the cutting edges of the drill to chip off new particles of stone at the bottom of the bore-hole at the next blow of thepercussion bar on the drill. To thisy end the Vpercussion bar 3 is `provided withl helical grooves 14: whichA at their lower vend merge into straight transmitting channels 15. The sleeve 12 engages the channels 14 by means of tongues 12 and in a similar sleeve 12 and the tool holder 13 are surrounded by a casing 16 which carries at its lower end the usual drill cage 17. The cylinder cover 10, the cylinder 1, and the casings 11 and 16 are kept in alignment and resilient contact with one another by lateral bolts 18, between whose nuts 18 and the lateral lugs 16 of the casing 1G helical springs 18 are inserted, as indicated by dotted lines in the drawing.

In order to impart to the drill the necessary am'ount ot rotation for the next cutting operation, as explained above, the stroke of the piston 2 and of the percussion bar 3 must attain its "full length. This cannot be the case when "the compression-which takes place after the cylinder chamber 7, or 8, is exhausted and the piston travels toward the cylinder cover 10, or the casing 11-commences too early, because in such cases the high compression removes the ball-valve t too early trom its seat. To avoid this I provide short narrow by-pass channels 19 and 20 which I have shown as arranged in the cylinder wall parallel to the axis ot the cylinder. Of these by-pass channels the `channel 19 is connected Vby its branches 21 and 22 with the interior of the cylinder', and the channel 20 is similarly connected therewith by means of its branches 23 and 24. Ot these branches the branch 22 is placed on a level with a radially disposed exhaust port 25 and the branch 23 is similarly placed on a. level with a likewise radially disposed exhaust port 26 in such a manner, that on the return stroke the edge 27 of the piston2 reaches the branch 22 at the same instant that it reaches the lower edge 28 of the exhaust port 25, whereas on the working stroke the bottom edge 29 ott the piston coincides simultaneously with the branch 23 of the by-pass channel 20 and with the upper edge 30 of the exhaust port 26. It is evident that the exhaust ports and by-pass channels may be of any suitable size, shape and number, but the length and the cross sectional area of these channels should be small so as to reduce the amount of air passing therethrough.

The periphery ofthe piston 2 is :provided with annular channels 31 and 32 and when the piston moves in the direction indicated by the arrows, the edge 27 reaches the mouth of the branch 22 and the'lower edge 28 of the exhaust port 25 simultaneously, as already indicated above. But when the piston travels slightly beyond the position shown .in the drawing it fully uncovers the branch 22 and shuts up or entraps spent motive fluid o1' atmospheric pressure in the circular cylinder chamber 7 from which it then escapes through `the by-pass channel 19, the annular channel 31 and the exhaust port 25, so that an after-exhaust trom the cylinder chamber' 7 is assured. This process of after-exhaustion continues without interruption until the mouth of the branch 21 of the by-pass channel 19 is completely overrun by the edge 27 o1 the piston, at which moment after-exhaust ceases. Vhen the piston 2 moves in the opposite direction the same action as described in connection with 'the circular cylinder chamber 7 will take place in regard to the annular cylinder chainber, because the by-pass channel20 connects this cylinder chamber with the exhaust port 26 in practically the same waythat ltheby-pass channel 19 connects the cylinder chamber 7 with the exhaust port 25.

'A close examination of the conditions under which the motive fluid is admitted into the cylinder 1, and of the 4influence the bypass channels 19 and 20exert upon them, will reveal the fact that 'the operation of the drill is to a certain extent detrimentally influenced by these by-pass channels, inasmuch as they permit the escape of live motive fluid from the cylinder. lThis 1loss,

of live motive Huid is, however, of little or no account, when `the by-pass channels 19 and 20 are ofthe right length. This `is the case when said length does not 'essentially exceed the distance intervening between, the one or the other of the piston faces andthe inner shoulder of the adjoining annular ypiston channel. Vhen for instance the moti-ve fluid is admitted to the `annular cylinder chamber 8 while the piston occupies the position shown in the drawing, 'the piston 2 uncovers on its return stroke the branch 24 of the by-pass channel 20. But since at this moment the branch 23 of this by-pass channel is brought into alignment with the annular `channel 32 of the piston it is -obvious that some of the live motive iuid destined to retract the piston 2 will escape from the cylinder chamber `8 through the exhaust port 26 during the short interval of time required to let the annular channel 32 pass over the branch 23 of the by-pass channel 20. This time interval'is so brief `that during this action the reduction of the cylinder pressure is inconsiderable, but this short time interval suiiieesV nevertheless for the after-exhaust from the cylinder chamber 8 when the piston travels in the opposite direction, i. e. when it is on its working stroke. i

Since the general operation of the rock drill is 'thoroughly known yin all its phases,

and besides this may be readily understood with the aid of the accompanylng drawing, a detailed description of it is deemed superluous.

I claim l. A pneumatic tool comprising a cylinder, a piston slidably mounted therein, means for admitting motive fluid to opposite end spaces of said cylinder so as to be alternately effective upon opposite faces of said piston to reciprocate the same in said cylinder, said piston being provided with two annular, peripheral channels, each located in spaced proximity to the contiguous end of said piston, said cylinder being provided with a pair of exhaust ports in s'pacedrelation to each other and further having by-pass channels each having its two ends terminating at the inner surface of said cylinder for establishing connection between said opposite end spaces ofthe cylinder, an annular channel of the piston and an exhaust port, the dis-` tance between the two ends of each by-pass channel being no greater than thevdistance between an end face of the piston and the contiguous annular channel thereof.

2. A pneumatic tool comprising a cylinder, a piston slidably mounted therein, means for admitting motive luid to opposite end spaces of said cylinder so as to be a1- ternately effective upon opposite faces of said piston to reciprocate the same in said cylinder, said piston being provided with two annular, peripheral channels, each located in spaced proximity to the contiguous end of said piston, said cylinder being provided with a pair of exhaust ports in spaced relation to each other and further having by-pass channels each having its two ends terminating at the inner surface of said cylinder for establishing connection between said opposite end spaces of the cylinder, an annular channel of the piston and an exhaust port, the distance between the two ends of each by-pass channel being approximately equal to the distance between an end face of the piston and the contiguous annular channel thereof. v

Signed by me at Cologne, Germany, at this 28th day ot' December 1922. f

JOSEF KHLEN. 

